Embryonic gonads immunostained as indicated in the figure. Anterior is to the left in each panel. (A,B) Wild-type st. 17 male gonads. msSGPs express ABD-B (A) and EYA (B) (arrows), in addition to SOX100B, whereas the ensheathing cells express only SOX100B. In this genetic background, a few posterior SGPs also express both SOX100B and ABD-B, as has been observed previously (DeFalco et al., 2003). (C,D) St. 17 XX (C) and XY (D) gonads from embryos expressing Kr-GAL4, UAS-GFP constructs on a TM3 balancer chromosome. GFP is expressed in cells ensheathing male gonads (arrowhead), but is not expressed in msSGPs (arrow). (E,F) Embryos homozygous for the HCJ199 allele of Abd-B. Male gonads lack msSGPs at both st. 15 (E) and st. 17 (F), but still exhibit SOX100B-positive ensheathing cells at st. 17. (G,H) Embryos expressing evestr3+7-GAL4 in combination with UAS-GFP and UAS-GAL4 for permanent lineage tracing. msSGPs (arrows) express GFP at st. 13 (G) and st. 17 (H) but SOX100B-positive ensheathing cells do not (arrowheads).